Recently, in order to ensure stability of power supply to various electric loads, an automotive power unit having a redundant functionality that enables the loads to be supplied with power from at least one of a plurality of storage batteries has been proposed.
In this type of power unit, when the voltage has decreased or a failure has occurred in one of the storage batteries, the loads are automatically supplied with power from the other storage batteries. JP 2013-95238A discloses a power unit that includes a battery and a capacitor which is charged with power supplied from a battery and serves as a backup power supply, and has a redundant functionality for supplying power to a load from the backup power supply if the output voltage of the battery has decreased.
In the power unit disclosed in JP 2013-95238A, the backup power supply cannot be charged if the battery has failed, and the power cannot be stably supplied to the load. Moreover, when a large current is supplied to the load, a voltage loss occurs due to a diode arranged on a redundant path, and heat is generated. Accordingly, the power unit in JP 2013-95238A is not suitable for supplying power to a load having a large current capacity.